Sennheiser Electronic GmbH & Co. KG
When the need for wireless monitoring solutions emerged in the 1990s, driven by the desire to make sound more controllable and remove clutter from stages, Sennheiser was perfectly placed to deliver solutions: With its expert background in RF wireless technology, the audio specialist started to custom-design IEM systems for both bands and soloists. With the advent of evolution wireless in 1999, Sennheiser offered its first series-produced wireless monitoring systems. Sennheiser’s IEM systems have been valued for their natural and clear sound ever since. The portfolio also includes the bestselling IE 100 PRO, IE 400 PRO and IE 500 PRO in-ear phones, which have been designed to come as close to custom moulds as possible, in respect of both sound and fit.
https://en-us.sennheiser.com/wireless-monitoring-system